WO2024122557A1

WO2024122557A1 - Ester compound, and ester compound composition for resin raw material

Info

Publication number: WO2024122557A1
Application number: PCT/JP2023/043565
Authority: WO
Inventors: 大地岡村; 嵩浩浅枝; 佑磨芝崎
Original assignee: 本州化学工業株式会社
Priority date: 2022-12-06
Filing date: 2023-12-06
Publication date: 2024-06-13
Also published as: WO2024122556A1

Abstract

The present invention addresses the problem of providing a curing agent that exhibits favorable handling properties and that imparts a cured product excelling in heat resistance and dielectric properties. As a solution, an ester compound represented by general formula (3) is provided.　[Chemical formula 1] (In general formula (3), each R₂ independently indicates a single bond or a C1-10 divalent hydrocarbon group, each R₃ independently indicates a hydrogen atom or a C1-6 alkyl group, and Y indicates a divalent group represented by general formula (3a) or general formula (3b).)　[Chemical formula 2] (In general formulas (3a) and (3b), each R₁ independently indicates a C1-6 alkyl group or a C6-12 aryl group, and each * indicates a bond position. In general formula (3a), each m independently indicates an integer of 1-4. In general formula (3b), each n independently indicates 0 or an integer of 1-4, and Z indicates a C7-20 cycloalkylidene group.)

Description

Ester compound, ester compound composition for resin raw material

The present invention relates to an ester compound and an ester compound composition for use as a resin raw material. More specifically, the present invention relates to an ester compound having a furan ring at both ends of a bonding group, and an ester compound composition for use as a resin raw material that contains the ester compound.

Epoxy resins have excellent heat resistance, adhesiveness, water resistance, mechanical strength and electrical properties, and are therefore used in a variety of fields, including adhesives, paints, composite materials, civil engineering and construction materials, insulating materials for electric and electronic parts, etc. In particular, in the electric and electronic field, they are widely used in insulating casting, laminating materials, sealing materials, etc.
Important properties required for epoxy resins, which are materials for electric and electronic components, include high heat resistance, low CTE, low dielectric constant, low dielectric loss tangent, low moisture absorption, etc. In addition, in highly integrated semiconductor materials, in recent years, there has been a trend toward high multi-layering, thinner insulating layers, and more complex structures, and a balance is required not only with the above-mentioned properties, but also with various other properties such as solvent solubility. Recently, a technology has been reported that aims to suppress polarization and improve low moisture absorption and dielectric properties by esterifying secondary hydroxyl groups generated by the reaction of epoxy groups with curing agents.
Patent Document 1 discloses a thermosetting composition that uses a thermoplastic resin obtained by esterifying the secondary hydroxyl groups of an epoxy resin in a post-process and blends a thermosetting resin therein, thereby improving adhesion to a conductor layer while maintaining low moisture absorption and dielectric properties; however, the heat resistance of the composition is insufficient.

International Publication No. 2005/095517

In view of the above-mentioned conventional techniques, the present invention aims to provide a curing agent that has good handling properties such as solvent solubility, and gives a cured product with excellent heat resistance and dielectric properties.

As a result of extensive research into solving the above problems, the inventors discovered that an ester compound of a bisphenol compound having a specific structure and a carboxylic acid having a furan ring dissolves in a solvent such as methyl ethyl ketone and is easy to handle, that using this as a curing agent causes a chain linkage by reacting with an epoxy resin, and that the chain linkage causes curing, and that the cured product obtained by esterifying the secondary hydroxyl groups has reduced polarization and has excellent dielectric properties and heat resistance, thus completing the present invention.

The present invention is as follows.
1. An ester compound represented by general formula (3):

(In the formula, each _R2 independently represents a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms, each _R3 independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and Y represents a divalent group represented by general formula (3a) or general formula (3b).

(In general formulas (3a) and (3b), R ₁ 's each independently represent an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and * represents a bonding position. In general formula (3a), m's each independently represent an integer of 1 to 4. In general formula (3b), n's each independently represent 0 or an integer of 1 to 4, and Z's each independently represent a cycloalkylidene group having 7 to 20 carbon atoms.)
2. The ester compound according to 1., wherein R ₂ in the ester compound represented by the general formula (3) is both a single bond.
3. The ester compound according to 2., wherein both R ₃ in the ester compound represented by the general formula (3) are hydrogen atoms.
4. The ester compound according to 3., wherein the ester compound represented by the general formula (3) is compound (p-139), (p-142), (p-145), (p-148), (p-151), (p-154) or (p-172).

5. A crystal of the ester compound of the compound (p-148) described in 4.
6. A crystal of the ester compound of the compound (p-148) described in 5., which has a maximum endothermic peak temperature in the range of 234 to 240° C. as determined by differential scanning calorimetry.
7.4. A crystal of the ester compound of the compound (p-151) described in Item 7.4.
8. A crystal of the ester compound of the compound (p-151) described in 7., which has a maximum endothermic peak temperature in the range of 180 to 188° C. as determined by differential scanning calorimetry.
9. An ester compound composition for a resin raw material, comprising an ester compound represented by the general formula (3) according to 9.1 and an ester compound represented by the general formula (2).

(In the formula, each R ₁ independently represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, each R ₆ independently represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, each X independently represents a single bond, an oxygen atom, a sulfur atom, a sulfonyl group, a carbonyl group, or a divalent group represented by general formula (1a), (1b), or (1c), and each n independently represents 0 or an integer of 1 to 4.)

(In general formulas (1a), (1b) and (1c), R ₄ and R ₅ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms; R ₄ and R ₅ may be bonded to each other to form a cycloalkylidene group having 5 to 20 carbon atoms as a whole; Ar ₁ and Ar ₂ each represent an aryl group having 6 to 12 carbon atoms; and * each indicates a bonding position.)
10. The ester compound composition for a resin raw material according to 9., which contains 0.1 to 400 parts by weight of the ester compound represented by the general formula (2) based on 100 parts by weight of the ester compound represented by the general formula (3).
Epoxy resin obtained by reacting an ester compound represented by general formula (3) described in 1. with any one selected from an aromatic diglycidyl ether compound, a mixture containing an aromatic dihydroxy compound and epihalohydrin, and a phenoxy resin having an epoxy group obtained by polymerizing an aromatic dihydroxy compound and epihalohydrin.

The ester compound of the present invention, represented by general formula (3) in which a specific bisphenol of the present invention is ester-bonded to a carboxylic acid having a furan ring, is soluble in a solvent such as methyl ethyl ketone and therefore has good handleability. In addition, when used as a curing agent, it reacts with an epoxy resin to form a chain linkage and cure. Furthermore, by esterifying the secondary hydroxyl group, polarization is suppressed, and a cured product having excellent dielectric properties and heat resistance can be provided.
For this reason, the ester compound represented by the general formula (3) of the present invention can be applied in various fields such as adhesives, composite materials, paints, civil engineering and building materials, and insulating materials for electric and electronic parts, and can give cured products that are useful as insulating castings, laminating materials, sealing materials, etc. in the electric and electronic fields.

FIG. 1 is a diagram showing a differential scanning calorimetry (DSC) curve of the ester compound (1-1) (compound (p-151)) obtained in Example 1. FIG. 2 is a diagram showing a differential scanning calorimetry (DSC) curve of the ester compound (1-2) (compound (p-28)) obtained in Example 2. FIG. 1 shows a differential scanning calorimetry (DSC) curve of the ester compound (1-3) (compound (p-148)) obtained in Example 3.

<Curable Composition>
The curable composition of the present invention contains an ester compound represented by general formula (1) and a thermosetting compound and/or a compound having a radically polymerizable substituent.

(In the formula, each R ₁ independently represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms; each R ₂ independently represents a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms; each R ₃ independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; each X independently represents a single bond, an oxygen atom, a sulfur atom, a sulfonyl group, a carbonyl group, or a divalent group represented by general formula (1a), (1b), or (1c); and each n independently represents 0 or an integer of 1 to 4.)

(In general formulas (1a), (1b) and (1c), R ₄ and R ₅ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms; R ₄ and R ₅ may be bonded to each other to form a cycloalkylidene group having 5 to 20 carbon atoms as a whole; Ar ₁ and Ar ₂ each represent an aryl group having 6 to 12 carbon atoms; and * each indicates a bonding position.)
By containing the ester compound represented by general formula (1), the cured product obtained by curing the curable composition has excellent heat resistance.
Among them, the ester compound represented by the general formula (1) reacts with the epoxy resin as a curing agent, particularly with respect to the secondary hydroxyl group generated by the reaction of the epoxy resin of the thermosetting compound with the curing agent, and by esterifying the secondary hydroxyl group, the resulting cured product has suppressed polarization and excellent dielectric properties. Therefore, the embodiment containing the epoxy resin in the curable composition of the present invention is useful and preferable because the resulting cured product has such characteristics. Also, for this reason, it is preferable to use the ester compound represented by the general formula (1) as a curing agent for the epoxy resin, because the resulting cured product has the above-mentioned characteristics.
Since the ester compound represented by the general formula (1) has a furan ring, it can also undergo a curing reaction with a compound having a radically polymerizable substituent to give a cured product.
The ester compound represented by the general formula (1) has excellent solubility in solvents such as methyl ethyl ketone, cyclohexanone, N-methylpyrrolidone, toluene, propylene glycol monomethyl ether acetate, and ethyl acetate, in particular, in methyl ethyl ketone, which is one of the solvents commonly used in the production of electronic components such as semiconductors, and therefore has excellent handleability.

(Ester compound represented by general formula (1))
In general formula (1), R ₁ 's each independently represent preferably an alkyl group having 1 to 4 carbon atoms or a phenyl group, more preferably a methyl group or a phenyl group, and particularly preferably a methyl group.
R ₂ in general formula (1) is independently a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms. In the case of a divalent hydrocarbon group, specific examples include a linear or branched alkylene group having 1 to 10 carbon atoms or an alkylene group containing a cyclic alkane, such as a methylene group, an ethylene group, a propane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a cyclohexane-1,3-diyl group, or a cyclohexane-1,4-diyl group; an alkylidene group having 1 to 10 carbon atoms, such as an ethylidene group, a propylidene group, an isopropylidene group, a butylidene group, a cyclopentylidene group, or a cyclohexylidene group; a phenylene group; and a divalent group having 1 to 10 carbon atoms containing a benzene ring, such as a group represented by the following formula:

(In the formula, * indicates the bond position.)
Among these, R ₂ are preferably each independently a single bond or a linear or branched alkylene group having 1 to 10 carbon atoms, an alkylene group containing a cyclic alkane, or an alkylidene group having 1 to 10 carbon atoms, more preferably each independently a single bond or a linear or branched alkylene group having 1 to 10 carbon atoms or an alkylene group containing a cyclic alkane, and even more preferably each independently a single bond or a linear or branched alkylene group having 1 to 6 carbon atoms or an alkylene group containing a cyclic alkane, and particularly preferably both are single bonds. The ester compound represented by general formula (1) in which R2 are both single bonds is also suitable in that a curable composition with an improved biomass ratio can be obtained because it is obtained from a raw material derived from biomass.
In formula (1), each R ₃ is preferably independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably independently a hydrogen atom or a methyl group, and particularly preferably both are a hydrogen atom.

X in general formula (1) is preferably a single bond, a sulfonyl group, a carbonyl group, or a divalent group represented by general formula (1a), (1b), or (1c), more preferably a single bond or a divalent group represented by general formula (1a) or general formula (1b), still more preferably a single bond or a divalent group represented by general formula (1a), and among the divalent groups represented by general formula (1a), R ₄ and R ₅ are each bonded to each other to form a divalent group having 5 to 20 carbon atoms as a whole, particularly preferably a single bond or a divalent group represented by general formula (1a).
When X in general formula (1) is general formula (1a), more preferable _R4 and _R5 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, further preferably each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a trifluoromethyl group, or an aryl group having 6 to 8 carbon atoms, and particularly preferably each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group.
R ₄ and R ₅ may be bonded to each other to form a cycloalkylidene group having 5 to 20 carbon atoms as a whole, and this embodiment is more preferable for R ₄ and R _5. The cycloalkylidene group having 5 to 20 carbon atoms may contain an alkyl group as a branched chain. The cycloalkylidene group preferably has 5 to 15 carbon atoms, more preferably has 6 to 12 carbon atoms, and particularly preferably has 6 to 9 carbon atoms. Specific examples of the cycloalkylidene group include a cyclopentylidene group (5 carbon atoms), a cyclohexylidene group (6 carbon atoms), a 3-methylcyclohexylidene group (7 carbon atoms), a 4-methylcyclohexylidene group (7 carbon atoms), a 3,3,5-trimethylcyclohexylidene group (9 carbon atoms), a cycloheptylidene group (7 carbon atoms), and a cyclododecanylidene group (12 carbon atoms). Preferred are a cyclohexylidene group (number of carbon atoms: 6), a 3-methylcyclohexylidene group (number of carbon atoms: 7), a 4-methylcyclohexylidene group (number of carbon atoms: 7), a 3,3,5-trimethylcyclohexylidene group (number of carbon atoms: 9), and a cyclododecanylidene group (number of carbon atoms: 12), and more preferred are a cyclohexylidene group (number of carbon atoms: 6), a 3,3,5-trimethylcyclohexylidene group (number of carbon atoms: 9), and a cyclododecanylidene group (number of carbon atoms: 12).
When X in formula (1) is formula (1b), preferred Ar ₁ and Ar ₂ are each independently a benzene ring or a naphthalene ring, and more preferably both Ar ₁ and Ar ₂ are benzene rings. For example, when both Ar ₁ and Ar ₂ are benzene rings, the group represented by formula (1b) is a fluorenylidene group.
When X in general formula (1) is general formula (1c), it is preferably a divalent group of 1,3-bis(isopropyl-2-yl)benzene or 1,4-bis(isopropyl-2-yl)benzene.
In general formula (1), the bonding positions of X and the two benzene rings are preferably each independently ortho- or para-positions, more preferably para-positions, with respect to the oxygen atom bonded to the benzene ring.
In the general formula (1), n is preferably each independently 0, 2, or 3. When n is an integer of 1 to 4, _R1 is preferably bonded at the ortho position with respect to the oxygen atom bonded to the benzene ring.

Specific examples of the ester compound represented by the general formula (1) include compounds (p-1) to (p-171) having the following chemical structures.

<Method for producing ester compound represented by general formula (1)>
There is no particular restriction on the starting material and the manufacturing method for the ester compound represented by the general formula (1). For example, as illustrated in the following reaction formula, a manufacturing method can be mentioned in which a bisphenol compound represented by the general formula (5) and an acid anhydride represented by the general formula (6) are reacted to synthesize an ester compound represented by the general formula (2) in an esterification step, and then the ester compound represented by the general formula (2) is reacted with a furan-containing carboxylic acid represented by the general formula (8) to obtain an ester compound represented by the general formula (1) in a transesterification step, as shown in the following reaction formula.

(R ₁ , X, and n in general formula (5), and R ₂ and R ₃ in general formula (8) are the same as those in general formula (1), and R ₆ in general formulas (6) and (7) is the same as that in general formula (2) described later.)

(Esterification step)
The reaction method in the esterification step in the above production method can be a conventionally known esterification reaction method.
Specific examples of the bisphenol compound represented by the general formula (5) include bisphenol F (bis(2-hydroxyphenyl)methane, 2-hydroxyphenyl-4-hydroxyphenylmethane, bis(4-hydroxyphenyl)methane), bisphenol E (1,1-bis(4-hydroxyphenyl)ethane), bisphenol A (2,2-bis(4-hydroxyphenyl)propane), bisphenol C (2,2-bis(4-hydroxy-3-methylphenyl)propane), 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3'-dimethylbiphenyl, 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl,4,4'-dihydroxy-2,2',3,3',5,5'-hexamethylbiphenyl, bis(4-hydroxyphenyl)ether, 4,4'-dihydroxybenzophenone, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfide, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)-1-naphthylethan, 2,2-bis(4-hydroxyphenyl)hexafluoro Examples of suitable bisphenols include propane, bisphenol Z (1,1-bis(4-hydroxyphenyl)cyclohexane), bisphenol TMC (1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane), 1,1-bis(4-hydroxyphenyl)-3-methylcyclohexane, 1,1-bis(4-hydroxyphenyl)-4-methylcyclohexane, 1,1-bis(4-hydroxyphenyl)cyclododecane, and 9,9-bis(4-hydroxy-3-methylphenyl)fluorene.
Specific examples of the acid anhydride represented by formula (6) include acetic anhydride and benzoic anhydride. The definition and preferred embodiments of _R6 in formula (6) are the same as those of formula (2) described below.
In the above production method, the amount of the acid anhydride represented by the general formula (6) used is preferably in the range of 2.0 to 10.0 mol, more preferably in the range of 2.0 to 8.0 mol, and even more preferably in the range of 2.0 to 4.0 mol, per 1 mol of the bisphenol compound represented by the general formula (5).
The reaction temperature is usually in the range of 50 to 150° C., preferably in the range of 80 to 140° C. The reaction pressure may be either normal pressure or reduced pressure.
The ester compound represented by the general formula (2) can be produced by the above esterification step.

(Ester compound represented by general formula (2))

(In the formula, R ₁ , X, and n are defined as in general formula (1), and each R ₆ independently represents a monovalent hydrocarbon group having 1 to 20 carbon atoms.)
In formula (2), R ₁ , X and n are the same as those in formula (1), and the preferred embodiments are also the same.
In general formula (2), R ₆ is preferably each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, more preferably each independently an alkyl group having 1 to 6 carbon atoms or a phenyl group, further preferably each independently a methyl group or a phenyl group, and particularly preferably a methyl group.
Specific examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms for R ₆ in general formula (2) include linear monovalent hydrocarbon groups such as a methyl group, an ethyl group, a propyl group, an isobutyl group, a butyl group, a hexyl group, an octyl group, and a decyl group, cyclic monovalent hydrocarbon groups such as a cyclohexyl group, and monovalent aromatic hydrocarbon groups such as a phenyl group and a naphthyl group.
The ester compound represented by general formula (2) obtained by the esterification step may be used as it is contained in the reaction solution of the esterification reaction as a raw material for the transesterification reaction step described later, or may be purified by distillation to remove the carboxylic acid represented by general formula (7) produced in the esterification reaction, or may be purified by mixing a solvent with the esterification reaction solution and subjecting it to a crystallization operation for use.

(Transesterification reaction process)
The reaction method in the transesterification step in the above production method can be a conventionally known transesterification method.
_R2 and _R3 in the general formula (8) are defined the same as in the general formula (1), and preferred embodiments and specific examples are also the same.
Specific examples of the furan-containing carboxylic acid represented by the general formula (8) include 2-furan carboxylic acid, 3-furan carboxylic acid, 2-methyl-3-furan carboxylic acid, and 3-methyl-2-furan carboxylic acid.
The amount of the furan-containing carboxylic acid represented by general formula (8) used is preferably in the range of 2.0 to 10.0 mol, more preferably in the range of 2.0 to 8.0 mol, and even more preferably in the range of 2.0 to 4.0 mol, relative to 1 mol of the ester compound represented by general formula (2).
It is preferable to use a base as a catalyst in the reaction of the ester compound represented by the general formula (2) with the furan-containing carboxylic acid represented by the general formula (8). Specific examples of such bases include organic bases such as amine bases, inorganic alkali metal compounds such as alkali metal hydroxides, carbonates, and hydrogen carbonate compounds, and organic alkali metal compounds such as alkali metal alcohols, phenols, and salts with organic carboxylic acids. Mixtures thereof may also be used, but are not limited thereto.
The reaction is usually carried out in the presence of a solvent. For reasons such as improved operability and reaction rate during industrial production, it is preferable to use a reaction solvent during the reaction. The solvent that can be used is not particularly limited as long as it does not distill from the reaction vessel at the reaction temperature described below and is inactive in the transesterification reaction. Specific examples include aromatic hydrocarbon ether solvents such as alkylaryl ethers such as phenetole and butylphenyl ether, diaryl ethers such as diphenyl ether and di-p-tolyl ether, aromatic hydrocarbon solvents such as biphenyl and terphenyl, alkyl-substituted naphthalenes such as diisopropylnaphthalene, aliphatic hydrocarbons such as decalin and kerosene, polyalkylene glycol ethers such as tetraethylene glycol dimethyl ether and diethylene glycol dibutyl ether, and organic solvents such as Therm-S series (manufactured by Nippon Steel Chemical Co., Ltd.), KSK-OIL series (manufactured by Soken Chemical Industry Co., Ltd.), or NeoSK-OIL series (manufactured by Soken Chemical Industry Co., Ltd.). The amount of the solvent used is not particularly limited as long as it does not interfere with the reaction, but is usually used in the range of 0.5 to 20 times by weight, preferably 1 to 10 times by weight, based on the ester compound represented by formula (2).
The reaction temperature is usually in the range of 40 to 260°C, preferably in the range of 80 to 255°C, more preferably in the range of 120 to 250°C, further preferably in the range of 160 to 245°C, particularly preferably in the range of 180 to 240°C.
The reaction may be carried out under normal pressure, or under increased or reduced pressure.
In another embodiment, the method may include a procedure for removing the carboxylic acid represented by the general formula (7) produced during the reaction from the reaction system. The procedure for removing the carboxylic acid represented by the general formula (7) produced from the reaction solution is not particularly limited, and the carboxylic acid can be removed by distilling the carboxylic acid represented by the general formula (7) produced together with the solvent system in the reaction solution. The carboxylic acid represented by the general formula (7) produced can be removed from the reaction system by using, for example, a pressure-equalizing dropping funnel equipped with a cock, a Dimroth condenser, a Dean-Stark apparatus, or the like.

After the reaction is completed, the ester compound represented by the general formula (1) can be obtained from the reaction mixture by a known method. For example, after the reaction, the reaction mixture can be cooled and crystallized, and filtered to obtain the target product in powder or granular form. Alternatively, the reaction mixture can be added to a poor solvent to obtain the target product by precipitation, or a solvent can be added to the reaction mixture to crystallize, and the product can be filtered to obtain the target product in powder or granular form.
The ester compound represented by the general formula (1) extracted by the above method can be made into a high-purity product by ordinary purification means such as washing with a solvent or water, recrystallization, etc. The solvent that can be used for crystallization and reslurry is not particularly limited as long as it is a solvent inert to the ester compound represented by the general formula (1), and specific examples thereof include alcohol-based solvents such as methanol, ethanol, isopropanol, and 1-butanol, carbonyl-based solvents such as acetic anhydride, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone, ether-based solvents such as tetrahydrofuran, methyl isobutyl ether, methyl isopropyl ether, and diphenyl ether, aromatic non-polar solvents such as toluene, xylene, and ethylbenzene, γ-butyrolactone, γ-valerolactone, acetonitrile, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. Among them, 1-butanol, isopropanol, and diphenyl ether are preferable.
The crystallization conditions vary depending on the solvent used and cannot be generally stated. For example, when 1-butanol is used, the amount of the solvent used is in the range of 1 part by weight to 50 parts by weight, more preferably 2 parts by weight to 30 parts by weight, and particularly preferably 2 to 10 parts by weight, per 1 part by weight of the total amount of the composition containing the ester compound represented by the general formula (1) to be purified and other impurities. The temperature during dissolution is in the range of 50 to 250°C, more preferably 70 to 230°C, even more preferably 80 to 200°C, and particularly preferably 90 to 180°C. The cooling temperature is in the range of 0°C to 50°C, more preferably 10 to 40°C, and even more preferably 15 to 35°C. The pressure during crystallization may be normal pressure conditions, or may be under pressure.
When using other solvents, various conditions can be appropriately changed taking into consideration the boiling point of the solvent, the solubility of the ester compound represented by general formula (1) to be purified, other impurities, and the composition containing them, etc.
The purified product obtained by these purification steps may contain the solvent used, so it is preferable to remove the solvent and dry it. The method for removing the solvent is not particularly limited, but examples include a method in which the solvent is distilled off by heating under normal pressure or reduced pressure.

<Ester compound represented by general formula (3)>
Among the ester compounds represented by general formula (1) used in the curable composition of the present invention, the ester compound represented by general formula (3) is preferred because the cured product obtained by using the curable composition of the present invention has better heat resistance.
Among them, in particular, for the secondary hydroxyl group generated by the reaction of the epoxy resin of the thermosetting compound with the curing agent, the ester compound represented by the general formula (3) reacts with the epoxy resin as a curing agent, similar to the ester compound represented by the general formula (1), and by esterifying the secondary hydroxyl group, the resulting cured product has suppressed polarization and excellent dielectric properties. For this reason, it is also preferable to use the ester compound represented by the general formula (3) as a curing agent for the epoxy resin, since the resulting cured product has the above-mentioned characteristics, similar to the ester compound represented by the general formula (1).
The ester compound represented by general formula (3), like the ester compound represented by general formula (1), has a furan ring, and can therefore undergo a curing reaction with a compound having a radically polymerizable substituent to give a cured product.
The ester compound represented by the general formula (3) has excellent solubility in solvents such as methyl ethyl ketone, cyclohexanone, N-methylpyrrolidone, toluene, propylene glycol monomethyl ether acetate, and ethyl acetate, in particular, in methyl ethyl ketone, which is one of the solvents commonly used in the production of electronic components such as semiconductors, and therefore has excellent handleability.

(In general formulas (3a) and (3b), R ₁ 's each independently represent an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and * represents a bonding position. In general formula (3a), m's each independently represent an integer of 1 to 4. In general formula (3b), n's each independently represent 0 or an integer of 1 to 4, and Z's each independently represent a cycloalkylidene group having 7 to 20 carbon atoms.)
Specific examples and preferred embodiments of _R2 and _R3 in general formula (3) are the same as _R2 and _R3 in general formula (1). That is, _R2 in general formula (3) is each independently a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms. Specific examples of divalent hydrocarbon groups include linear or branched alkylene groups having 1 to 10 carbon atoms or alkylene groups containing a cyclic alkane, such as a methylene group, an ethylene group, a propane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a cyclohexane-1,3-diyl group, or a cyclohexane-1,4-diyl group; alkylidene groups having 1 to 10 carbon atoms, such as an ethylidene group, a propylidene group, an isopropylidene group, a butylidene group, a cyclopentylidene group, or a cyclohexylidene group; phenylene groups; and divalent groups having 1 to 10 carbon atoms containing a benzene ring, such as groups represented by the following formulas:

(In the formula, * indicates the bond position.)
Among these, R ₂ are preferably each independently a single bond or a linear or branched alkylene group having 1 to 10 carbon atoms, an alkylene group containing a cyclic alkane, or an alkylidene group having 1 to 10 carbon atoms, more preferably each independently a single bond or a linear or branched alkylene group having 1 to 10 carbon atoms or an alkylene group containing a cyclic alkane, and even more preferably each independently a single bond or a linear or branched alkylene group having 1 to 6 carbon atoms or an alkylene group containing a cyclic alkane, and particularly preferably both are single bonds. The ester compound represented by general formula (3) in which R ₂ are both single bonds is also suitable in that a curable composition with an improved biomass ratio can be obtained because it is obtained from a raw material derived from biomass.
In formula (3), each R ₃ is preferably independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably independently a hydrogen atom or a methyl group, and particularly preferably both are a hydrogen atom.
When Y in formula (3) is formula (3a), the preferred embodiment of _R1 is the same as _R1 in formula (1). That is, when Y in formula (3) is formula (3a), _R1 in formula (3a) is preferably each independently an alkyl group having 1 to 4 carbon atoms or a phenyl group, more preferably each independently a methyl group or a phenyl group, and particularly preferably a methyl group.
When Y in general formula (3) is general formula (3a), m each independently represents an integer of 1 to 4, preferably each independently represents an integer of 1 to 3, more preferably each independently represents 2 or 3, and particularly preferably both represent 3. It is preferable that _R1 is preferentially bonded to the ortho position with respect to the oxygen atom bonded to the benzene ring.
A more preferred embodiment in which Y in general formula (3) is general formula (3a) is a structure selected from general formulas (3a-1) to (3a-4), more preferably a structure selected from general formulas (3a-2) to (3a-4), further preferably general formula (3a-3) or (3a-4), and particularly preferably general formula (3a-4).

(In the formula, each R ₁ independently represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and * indicates the bonding position.)
When Y in formula (3) is formula (3b), the preferred embodiment of R ₁ is the same as the preferred embodiment of R ₁ in formula (1). That is, when Y in formula (3) is formula (3b), R ₁ in formula (3b) is preferably each independently an alkyl group having 1 to 4 carbon atoms or a phenyl group, more preferably each independently a methyl group or a phenyl group, and particularly preferably a methyl group.
When Y in formula (3) is formula (3b), n is preferably 0, 1 or 2, more preferably 0 or 1, and particularly preferably both are 0. The substitution position of _R1 is preferably the ortho position relative to the oxygen atom.
Z in general formula (3b) represents a cycloalkylidene group having 7 to 20 carbon atoms, which may have an alkyl group as a branched chain. Such a cycloalkylidene group preferably has 7 to 15 carbon atoms, more preferably has 7 to 12 carbon atoms, and particularly preferably has 7 to 9 carbon atoms. Specific examples of such cycloalkylidene groups include a 3-methylcyclohexylidene group (7 carbon atoms), a 4-methylcyclohexylidene group (7 carbon atoms), a 3,3,5-trimethylcyclohexylidene group (9 carbon atoms), and a cyclododecanylidene group (12 carbon atoms). Preferred is a 3-methylcyclohexylidene group (number of carbon atoms: 7), a 4-methylcyclohexylidene group (number of carbon atoms: 7) or a 3,3,5-trimethylcyclohexylidene group (number of carbon atoms: 9), more preferred is a 3-methylcyclohexylidene group (number of carbon atoms: 7) or a 3,3,5-trimethylcyclohexylidene group (number of carbon atoms: 9), and particularly preferred is a 3,3,5-trimethylcyclohexylidene group (number of carbon atoms: 9).
Specific examples of the ester compound represented by the general formula (3) include compounds (p-139) to (p-177) having the following chemical structures.
The ester compound represented by general formula (3) is preferably one compound selected from the compounds (p-139) to (p-177), and among these, the compound (p-139), (p-142), (p-145), (p-148), (p-151), (p-154) or (p-172) is particularly preferable.

<Method for producing ester compound represented by formula (3)>
The ester compound of the present invention represented by the general formula (3) can be produced in the same manner as in the production of the ester compound represented by the general formula (1).
Specifically, there is no particular restriction on the starting material and manufacturing method for the ester compound represented by the general formula (3). For example, as illustrated in the following reaction formula, a manufacturing method can be mentioned in which a bisphenol compound represented by the general formula (9) and an acid anhydride represented by the general formula (6) are reacted to synthesize an ester compound represented by the general formula (10) in an esterification step, and then the ester compound represented by the general formula (10) is reacted with a furan-containing carboxylic acid represented by the general formula (8) to obtain an ester compound represented by the general formula (3) in a transesterification step.

(Y in general formulas (9) and (10) is the same as defined in general formula (3), _R2 and _R3 in general formula (8) are the same as defined in general formula (1), and _R6 in general formulas (6), (7) and (10) is the same as defined in general formula (2).)

(Esterification step)
The reaction method in the esterification step in the above production method can be a conventionally known esterification reaction method.
As the bisphenol compound represented by the general formula (9), specific examples of the compound in which Y is the general formula (3a) include 4,4'-dihydroxy-3,3'-dimethylbiphenyl, 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl, and 4,4'-dihydroxy-2,2',3,3'5,5'-hexamethylbiphenyl. Specific examples of the compound in which Y is the general formula (3b) include bisphenol TMC (1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane), 1,1-bis(4-hydroxyphenyl)-3-methylcyclohexane, 1,1-bis(4-hydroxyphenyl)-4-methylcyclohexane, and 1,1-bis(4-hydroxyphenyl)cyclododecane.
Specific examples of the acid anhydride represented by the general formula (6) include acetic anhydride and benzoic anhydride.
In the above production method, the amount of the acid anhydride represented by the general formula (6) used is preferably in the range of 2.0 to 10.0 mol, more preferably in the range of 2.0 to 8.0 mol, and even more preferably in the range of 2.0 to 4.0 mol, per 1 mol of the bisphenol compound represented by the general formula (9).
The reaction temperature is usually in the range of 50 to 150° C., preferably in the range of 80 to 140° C. The reaction pressure may be either normal pressure or reduced pressure.
The ester compound represented by the general formula (10) can be produced by the above esterification step.
The definition of Y in formula (10) is the same as in formula (3), and the preferred embodiments are also the same.
_R6 in formula (10) is defined the same as in formula (2), and specific examples and preferred embodiments thereof are also the same.
The ester compound represented by general formula (10) obtained by the esterification step may be used as it is contained in the reaction solution of the esterification reaction as a raw material for the transesterification reaction step described later, or may be purified by distillation to remove the carboxylic acid represented by general formula (7) produced in the esterification reaction, or may be purified by mixing a solvent with the esterification reaction solution and subjecting it to a crystallization operation for use.

(Transesterification reaction process)
The reaction method in the transesterification step in the above production method can be a conventionally known transesterification method.
_R2 and _R3 in the general formula (8) are defined the same as in the general formula (1), and preferred embodiments and specific examples are also the same.
Specific examples of the furan-containing carboxylic acid represented by the general formula (8) include 2-furan carboxylic acid, 3-furan carboxylic acid, 2-methyl-3-furan carboxylic acid, and 3-methyl-2-furan carboxylic acid.
The amount of the furan-containing carboxylic acid represented by general formula (8) used is preferably in the range of 2.0 to 10.0 mol, more preferably in the range of 2.0 to 8.0 mol, and even more preferably in the range of 2.0 to 4.0 mol, relative to 1 mol of the ester compound represented by general formula (10).
It is preferable to use a base as a catalyst in the reaction of the ester compound represented by the general formula (10) with the furan-containing carboxylic acid represented by the general formula (8). Specific examples of such bases include organic bases such as amine bases, inorganic alkali metal compounds such as alkali metal hydroxides, carbonates, and hydrogen carbonate compounds, and organic alkali metal compounds such as alkali metal alcohols, phenols, and salts with organic carboxylic acids. Mixtures thereof may also be used, but are not limited thereto.
The reaction is usually carried out in the presence of a solvent. For reasons such as improved operability and reaction rate during industrial production, it is preferable to use a reaction solvent during the reaction. The solvent that can be used is not particularly limited as long as it does not distill from the reaction vessel at the reaction temperature described below and is inactive in the transesterification reaction. Specific examples include aromatic hydrocarbon ether solvents such as alkylaryl ethers such as phenetole and butylphenyl ether, diaryl ethers such as diphenyl ether and di-p-tolyl ether, aromatic hydrocarbon solvents such as biphenyl and terphenyl, alkyl-substituted naphthalenes such as diisopropylnaphthalene, aliphatic hydrocarbons such as decalin and kerosene, polyalkylene glycol ethers such as tetraethylene glycol dimethyl ether and diethylene glycol dibutyl ether, and organic solvents such as Therm-S series (manufactured by Nippon Steel Chemical Co., Ltd.), KSK-OIL series (manufactured by Soken Chemical Industry Co., Ltd.), or NeoSK-OIL series (manufactured by Soken Chemical Industry Co., Ltd.). The amount of the solvent used is not particularly limited as long as it does not interfere with the reaction, but is usually used in the range of 0.5 to 20 times by weight, preferably 1 to 10 times by weight, based on the ester compound represented by formula (10).
The reaction temperature is usually in the range of 40 to 260°C, preferably in the range of 80 to 255°C, more preferably in the range of 120 to 250°C, further preferably in the range of 160 to 245°C, particularly preferably in the range of 180 to 240°C.
The reaction may be carried out under normal pressure, or under increased or reduced pressure.
In another embodiment, the method may include a procedure for removing the carboxylic acid represented by the general formula (7) produced during the reaction from the reaction system. The procedure for removing the carboxylic acid represented by the general formula (7) produced from the reaction solution is not particularly limited, and the carboxylic acid can be removed by distilling the carboxylic acid represented by the general formula (7) produced together with the solvent system in the reaction solution. The carboxylic acid represented by the general formula (7) produced can be removed from the reaction system by using, for example, a pressure-equalizing dropping funnel equipped with a cock, a Dimroth condenser, a Dean-Stark apparatus, or the like.

After the reaction is completed, the ester compound represented by the general formula (3) can be obtained from the reaction mixture by a known method. For example, after the reaction, the reaction mixture can be cooled and crystallized, and filtered to obtain the target product in powder or granular form. Alternatively, the reaction mixture can be added to a poor solvent to obtain the target product by precipitation, or a solvent can be added to the reaction mixture to cause crystallization, and the product can be filtered to obtain the target product in powder or granular form.
The ester compound represented by the general formula (3) extracted by the above method can be made into a high-purity product by ordinary purification means such as washing with a solvent or water, recrystallization, etc. The solvent that can be used for crystallization and reslurry is not particularly limited as long as it is a solvent inert to the ester compound represented by the general formula (3), and specific examples thereof include alcohol-based solvents such as methanol, ethanol, isopropanol, and 1-butanol, carbonyl-based solvents such as acetic anhydride, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone, ether-based solvents such as tetrahydrofuran, methyl isobutyl ether, methyl isopropyl ether, and diphenyl ether, aromatic nonpolar solvents such as toluene, xylene, and ethylbenzene, γ-butyrolactone, γ-valerolactone, acetonitrile, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. Among them, 1-butanol, isopropanol, and diphenyl ether are preferable.
The crystallization conditions vary depending on the solvent used and cannot be generally stated. For example, when 1-butanol is used, the amount of the solvent used is in the range of 1 part by weight to 50 parts by weight, more preferably 2 parts by weight to 30 parts by weight, and particularly preferably 2 to 10 parts by weight, per 1 part by weight of the total amount of the composition containing the ester compound represented by the general formula (3) to be purified and other impurities. The temperature during dissolution is in the range of 50 to 250°C, more preferably 70 to 230°C, even more preferably 80 to 200°C, and particularly preferably 90 to 180°C. The cooling temperature is in the range of 0°C to 50°C, more preferably 10 to 40°C, and even more preferably 15 to 35°C. The pressure during crystallization may be normal pressure conditions, or may be under pressure.
When using other solvents, various conditions can be appropriately changed taking into consideration the boiling point of the solvent, the solubility of the ester compound represented by general formula (3) to be purified, other impurities, and the composition containing them, etc.
The purified product obtained by these purification steps may contain the solvent used, so it is preferable to remove the solvent and dry it. The method for removing the solvent is not particularly limited, but examples include a method in which the solvent is distilled off by heating under normal pressure or reduced pressure.

<Crystals of compound (p-148)>
Among the ester compounds of the present invention, the crystals of the compound represented by formula (p-148) can be handled as a crystalline solid and are therefore very useful since they have excellent handleability.
The crystals preferably have a maximum endothermic peak temperature in the range of 234 to 240°C, more preferably 235 to 240°C, and particularly preferably 236 to 239°C, as determined by differential scanning calorimetry.

<Method for producing crystals of compound (p-148)>
The compound (p-148) produced by the method for producing an ester compound represented by the above general formula (3) can be produced by crystallization from a solvent containing an alcohol solvent such as methanol, ethanol, isopropanol, 1-butanol, etc., particularly an alcohol solvent having 1 to 4 carbon atoms, and an ether solvent such as tetrahydrofuran, methyl isobutyl ether, methyl isopropyl ether, diphenyl ether, etc., particularly an ether solvent having 4 to 12 carbon atoms.
Of the alcohol solvents having 1 to 4 carbon atoms, 1-butanol and isopropanol are particularly preferred, and of the ether solvents having 4 to 12 carbon atoms, diphenyl ether is particularly preferred.
The crystallization conditions are such that the total amount of the alcohol solvent and the ether solvent is in the range of 1 to 50 parts by weight, more preferably 2 to 30 parts by weight, and particularly preferably 2 to 10 parts by weight, per 1 part by weight of the total amount of the composition containing the compound (p-148) and other post-reaction impurities.
Regarding the ratio of the alcohol solvent to the ether solvent, the amount of the ether solvent used relative to the amount of the alcohol solvent used is preferably 0.3 to 3.0 times by weight, more preferably 0.5 to 2.5 times by weight, even more preferably 1.0 to 2.2 times by weight, and particularly preferably 1.4 to 2.2 times by weight.
The temperature during dissolution is in the range of 50 to 250° C., more preferably in the range of 70 to 230° C., even more preferably in the range of 80 to 200° C., and particularly preferably in the range of 90 to 180° C. The cooling temperature is in the range of 0 to 50° C., more preferably in the range of 10 to 40° C., and even more preferably in the range of 15 to 35° C. The pressure during crystallization may be normal pressure or may be increased.
Since the crystals obtained by crystallization may contain the solvent used, it is preferable to remove the solvent and dry the crystals. The method for removing the solvent is not particularly limited, but examples thereof include a method in which the solvent is distilled off by heating under normal pressure or reduced pressure.

<Crystals of compound (p-151)>
Among the ester compounds of the present invention, the crystals of the compound represented by formula (p-151) can be handled as a crystalline solid and are therefore very useful since they have excellent handleability.
The crystals preferably have a maximum endothermic peak temperature in the range of 180 to 188°C, more preferably 181 to 187°C, and particularly preferably 182 to 186°C, as determined by differential scanning calorimetry.

<Method for producing crystals of compound (p-151)>
The compound (p-151) produced by the method for producing the ester compound represented by the above general formula (3) can be produced by crystallization from an alcohol solvent such as methanol, ethanol, isopropanol, 1-butanol, etc., particularly a solvent containing an alcohol solvent having 1 to 4 carbon atoms.
Of the alcohol solvents having 1 to 4 carbon atoms, 1-butanol and isopropanol are particularly preferred.
Regarding the crystallization conditions, the amount of the alcohol solvent used is in the range of 1 part by weight to 50 parts by weight, more preferably 2 parts by weight to 30 parts by weight, and particularly preferably 2 parts by weight to 10 parts by weight, per 1 part by weight of the total amount of the composition containing the compound (p-151) and other post-reaction impurities.
The temperature during dissolution is in the range of 50 to 250° C., more preferably in the range of 70 to 230° C., even more preferably in the range of 80 to 200° C., and particularly preferably in the range of 90 to 180° C. The cooling temperature is in the range of 0 to 50° C., more preferably in the range of 10 to 40° C., and even more preferably in the range of 15 to 35° C. The pressure during crystallization may be normal pressure or may be increased.
Since the crystals obtained by crystallization may contain the solvent used, it is preferable to remove the solvent and dry the crystals. The method for removing the solvent is not particularly limited, but examples thereof include a method in which the solvent is distilled off by heating under normal pressure or reduced pressure.

<Ester compound composition for resin raw material>
The ester compound represented by the general formula (3) can also be used in the form of a resin raw material composition containing an ester compound represented by the general formula (2).
The ester compound represented by general formula (2) further contained in the resin raw material composition may be an ester compound represented by general formula (10), and this is more preferable.
This resin raw material composition contains preferably 0.1 to 400 parts by weight, more preferably 0.1 to 200 parts by weight, even more preferably 0.1 to 150 parts by weight, still more preferably 0.1 to 100 parts by weight, and particularly preferably 0.1 to 10 parts by weight of the ester compound represented by general formula (2) relative to 100 parts by weight of the ester compound represented by general formula (3).
The resin raw material composition of the present invention can be produced by mixing the ester compound represented by general formula (3) and the ester compound represented by general formula (2) which have been separately produced, so as to obtain a desired amount, or can be produced by using the ester compound represented by general formula (2) as an intermediate for producing the ester compound represented by general formula (3) and adjusting the reaction rate of the transesterification reaction with the furan-containing carboxylic acid represented by general formula (8) so as to obtain a desired amount.

The ester compound composition for resin raw material containing the ester compound represented by the general formula (3) and the ester compound represented by the general formula (2) can be used to produce a cured product by reacting it with a thermosetting compound and/or a compound having a radically polymerizable substituent, for example, as in a curable composition described later. Also, in the production of an epoxy resin obtained by reacting an ester compound represented by the general formula (3) described later, an ester compound composition for resin raw material further containing an ester compound represented by the general formula (2) can be used.

<Epoxy resin obtained by reaction of an ester compound represented by general formula (3)>
The ester compound of the present invention represented by the general formula (3) can be reacted with an aromatic diglycidyl ether compound (e.g., a compound in which a hydroxyl group of a bisphenol compound represented by the general formula (5) or the like is glycidylated) to obtain an epoxy resin. In order to facilitate the progress of high molecular weight polymerization in a state in which an epoxy group is present at the molecular end, it is preferable to carry out the reaction using an amount in which the compounding equivalent ratio is in the range of (epoxy group):(ester group)=1 to 1.2:1.
Examples of epoxy resins obtained by reacting an ester compound represented by general formula (3) include epoxy resins obtained by reacting a mixture containing an aromatic dihydroxy compound and epihalohydrin, and epoxy resins obtained by reacting an aromatic dihydroxy compound with a phenoxy resin having an epoxy group obtained by polymerizing an aromatic dihydroxy compound with epihalohydrin.
That is, the epoxy resin obtained by reacting the ester compound represented by the general formula (3) may be an epoxy resin obtained by reacting the ester compound represented by the general formula (3) with any one selected from an aromatic diglycidyl ether compound, a mixture containing an aromatic dihydroxy compound and epihalohydrin, and a phenoxy resin having an epoxy group obtained by polymerizing an aromatic dihydroxy compound and epihalohydrin.

(Method for producing an epoxy resin by reacting an ester compound represented by general formula (3))
A catalyst may be used in the synthesis of an epoxy resin obtained by reacting an ester compound represented by the general formula (3), and the catalyst may be any compound having a catalytic ability to promote the reaction between an epoxy group and an ester group, such as tertiary amines, cyclic amines, imidazoles, organic phosphorus compounds, and quaternary ammonium salts.
Specific examples of tertiary amines include triethylamine, tri-n-propylamine, tri-n-butylamine, triethanolamine, benzyldimethylamine, pyridine, and 4-(dimethylamino)pyridine.
Specific examples of cyclic amines include 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]-7-undecene, and 1,5-diazabicyclo[4,3,0]-5-nonene.
Specific examples of the imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole.
Specific examples of the organic phosphorus compound include tri-n-propylphosphine, tri-n-butylphosphine, triphenylphosphine, tris(p-tolyl)phosphine, tricyclohexylphosphine, tri(tert-butyl)phosphine, tris(p-methoxyphenyl)phosphine, tetramethylphosphonium bromide, tetramethylphosphonium iodide, tetramethylphosphonium hydroxide, tetrabutylphosphonium hydroxide, trimethylcyclohexylphosphonium chloride, trimethylcyclohexylphosphonium bromide, trimethylbenzylphosphonium chloride, trimethylbenzylphosphonium bromide, tetraphenylphosphonium bromide, triphenylmethylphosphonium bromide, triphenylmethylphosphonium iodide, triphenylethylphosphonium chloride, triphenylethylphosphonium bromide, triphenylethylphosphonium iodide, triphenylbenzylphosphonium chloride, and triphenylbenzylphosphonium bromide.
Among the catalysts listed above, 4-(dimethylamino)pyridine, 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]-7-undecene, 1,5-diazabicyclo[4,3,0]-5-nonene, 2-ethyl-4-methylimidazole, tris(p-tolyl)phosphine, tricyclohexylphosphine, tri(tert-butyl)phosphine, and tris(p-methoxyphenyl)phosphine are preferred, and 4-(dimethylamino)pyridine, 1,8-diazabicyclo[5,4,0]-7-undecene, 1,5-diazabicyclo[4,3,0]-5-nonene, and 2-ethyl-4-methylimidazole are particularly preferred. The catalysts may be used alone or in combination of two or more.
The amount of the catalyst used is in the range of 0.001 to 3% by weight based on the amount of the reaction substrate used in the reaction to obtain an epoxy resin obtained by reacting an ester compound represented by general formula (3). When these compounds are used as catalysts, they remain as catalyst residues in the obtained curable composition, which may deteriorate the insulating properties of the printed wiring board or shorten the pot life of the composition. Therefore, when a nitrogen-containing compound is used as a catalyst, the nitrogen content in the curable composition is preferably 2000 ppm or less, more preferably 1000 ppm or less. When a phosphorus-containing compound is used as a catalyst, the phosphorus content in the curable composition is preferably 2000 ppm or less, more preferably 1000 ppm or less.

In the synthesis reaction step of producing an epoxy resin obtained by reacting an ester compound represented by the general formula (3) according to the present invention, a reaction solvent may be used, and the solvent may be any solvent that dissolves the epoxy resin. Examples of the solvent include aromatic hydrocarbon solvents, ketone solvents, amide solvents, and glycol ether solvents. The solvent may be used alone or in combination of two or more.
Specific examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, etc. Specific examples of ketone solvents include acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, 2-heptanone, 4-heptanone, 2-octanone, cyclohexanone, acetylacetone, dioxane, etc.
Specific examples of amide solvents include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, 2-pyrrolidone, and N-methylpyrrolidone.
Specific examples of glycol ether solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol mono-n-butyl ether, and propylene glycol monomethyl ether acetate.

The solid content in the synthesis reaction during the production of the epoxy resin is preferably 10 to 95% by weight. If a highly viscous product is produced during the reaction, the reaction can be continued by adding additional solvent. After the reaction is completed, the solvent can be removed or further added as necessary.
In the production of epoxy resins, the polymerization reaction is carried out at a reaction temperature at which the catalyst used does not decompose. If the reaction temperature is too high, the catalyst may decompose, causing the reaction to stop, or the epoxy resin produced may deteriorate. Conversely, if the temperature is too low, the reaction may not proceed sufficiently. For these reasons, the reaction temperature is preferably 50 to 250°C, more preferably 120 to 230°C. The reaction time is usually 1 to 12 hours, preferably 3 to 10 hours. When a low-boiling point solvent such as acetone or methyl ethyl ketone is used, the reaction temperature can be ensured by carrying out the reaction under high pressure using an autoclave.

The ester compound represented by the general formula (3) is included in the ester compound represented by the general formula (1) and can be used in the same manner, so the ester compound represented by the general formula (1) will be described below.
Hereinafter, an invention in which the ester compound represented by general formula (1) is replaced with an ester compound represented by general formula (3) is also disclosed.

The curable composition of the present invention contains an ester compound represented by general formula (1), a thermosetting compound, and/or a compound having a radical polymerizable substituent. That is, the curable composition of the present invention may be embodied in the following manner: an ester compound represented by general formula (1) and a thermosetting compound, an ester compound represented by general formula (1) and a compound having a radical polymerizable substituent, or an ester compound represented by general formula (1), a thermosetting compound, and a compound having a radical polymerizable substituent.
In order to compensate for or further improve the deficiencies in the physical properties and characteristics of the curable composition of the present invention and the cured product obtained therefrom, a person skilled in the art who has come into contact with the present invention can appropriately and suitably select the above-mentioned embodiment, select or change the compounds to be used, and adjust the amounts used, etc., within the scope disclosed in the present invention and the scope that is self-evident.

The ester compound represented by general formula (1) used in the curable composition of the present invention may be one type of compound falling within the scope of the formula, or two or more types may be used in combination.

The ester compound represented by general formula (1) used in the curable composition of the present invention can also be used in the form of a curable composition further containing an ester compound represented by general formula (2).
In this case, the ester compound represented by the general formula (2) is contained in an amount of preferably 0.1 to 400 parts by weight, more preferably 0.1 to 200 parts by weight, even more preferably 0.1 to 150 parts by weight, still more preferably 0.1 to 100 parts by weight, and particularly preferably 0.1 to 10 parts by weight, relative to 100 parts by weight of the ester compound represented by the general formula (1).
The ester compound represented by the general formula (1) and the ester compound represented by the general formula (2) which have been separately produced can be mixed to obtain a desired amount, or the ester compound represented by the general formula (2) can be used as an intermediate for producing the ester compound represented by the general formula (1) and the reaction rate of the transesterification reaction with the furan-containing carboxylic acid represented by the general formula (8) can be adjusted to obtain a desired amount.

<Thermosetting Compound>
The thermosetting compound used in the curable composition of the present invention may be any conventionally known thermosetting compound. Specific examples include one or more compounds selected from the group consisting of epoxy resins, benzoxazine compounds, benzoxazine resins, phenolic resins, bismaleimide compounds, and maleimide resins.
As the epoxy resin, the benzoxazine compound, the benzoxazine resin, the phenolic resin, the bismaleimide compound, and the maleimide resin, any compound including conventionally known compounds can be used.

(Epoxy resin)
The epoxy resin includes phenoxy resins having epoxy groups obtained by polymerizing glycidyl ether compounds, aromatic diglycidyl ether compounds (e.g., compounds obtained by glycidylating hydroxyl groups of hydroquinone, resorcinol, catechol, bisphenol compounds represented by general formula (5) and the like), aromatic dihydroxy compounds (e.g., hydroquinone, resorcinol, catechol, bisphenol compounds represented by general formula (5) and the like) and epihalohydrin with or without the use of an active ester-based curing agent, and any epoxy resin including a conventionally known compound can be used. As such an active ester-based curing agent, an epoxy resin obtained by reacting an ester compound represented by general formula (1) according to the present invention can also be used, and it is preferable to use this. These can be used alone or as a mixture of two or more kinds.
The conventionally known epoxy resin used is preferably one having two or more epoxy groups in the molecule. For example, various epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AF type epoxy resin, bisphenol Z type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, triphenylmethane type epoxy resin, dicyclopentadiene type epoxy resin, and phenoxy resin can be used.
When the epoxy resin obtained by reacting the ester compound represented by the general formula (1) is used in combination with another epoxy resin, the amount of the other epoxy resin in the total epoxy resin component is preferably 1% by weight or more, more preferably 5% by weight or more, and even more preferably 10% by weight or more, while it is preferably 99% by weight or less, more preferably 95% by weight or less, and even more preferably 90% by weight or less. By having the ratio of the other epoxy resin be equal to or more than the above lower limit, the effect of improving the physical properties by blending the other epoxy resin can be sufficiently obtained. On the other hand, by having the ratio of the other epoxy resin be equal to or less than the above upper limit, the effect of the epoxy resin of the present invention is sufficiently exhibited, which is preferable from the viewpoint of obtaining film formability.
The amount of the epoxy resin obtained by reacting the ester compound represented by the general formula (1) or other epoxy resin used is based on the amount excluding the solvent when the solvent is contained.

(Epoxy resin obtained by reacting an ester compound represented by general formula (1))
The epoxy resin obtained by reacting the ester compound represented by the general formula (1) of the present invention can be obtained, for example, by reacting an aromatic diglycidyl ether compound (e.g., a compound in which a hydroxyl group is glycidylated, such as hydroquinone, resorcinol, catechol, or a bisphenol compound represented by the general formula (5)) with the ester compound represented by the general formula (1). In order to facilitate the progress of high molecular weight in a state in which the epoxy group is present at the molecular end, it is preferable to carry out the reaction using an amount used in which the compounding equivalent ratio is in the range of (epoxy group):(ester group)=1 to 1.2:1.
Other examples of the method include a method of reacting a mixture containing an aromatic dihydroxy compound and epihalohydrin with an ester compound represented by general formula (1), and a method of reacting a phenoxy resin having an epoxy group obtained by polymerizing an aromatic dihydroxy compound and epihalohydrin with an ester compound represented by general formula (1).
That is, the epoxy resin obtained by reacting the ester compound represented by the general formula (1) may be an epoxy resin obtained by reacting the ester compound represented by the general formula (1) with any one selected from an aromatic diglycidyl ether compound, a mixture containing an aromatic dihydroxy compound and epihalohydrin, and a phenoxy resin having an epoxy group obtained by polymerizing an aromatic dihydroxy compound and epihalohydrin.

A catalyst may be used in the synthesis of an epoxy resin obtained by reacting an ester compound represented by general formula (1), and the catalyst may be any compound having a catalytic ability to promote the reaction between an epoxy group and an ester group, such as tertiary amines, cyclic amines, imidazoles, organic phosphorus compounds, and quaternary ammonium salts.
Specific examples of tertiary amines include triethylamine, tri-n-propylamine, tri-n-butylamine, triethanolamine, benzyldimethylamine, pyridine, and 4-(dimethylamino)pyridine.
Specific examples of cyclic amines include 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]-7-undecene, and 1,5-diazabicyclo[4,3,0]-5-nonene.
Specific examples of the imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole.
Specific examples of the organic phosphorus compound include tri-n-propylphosphine, tri-n-butylphosphine, triphenylphosphine, tris(p-tolyl)phosphine, tricyclohexylphosphine, tri(tert-butyl)phosphine, tris(p-methoxyphenyl)phosphine, tetramethylphosphonium bromide, tetramethylphosphonium iodide, tetramethylphosphonium hydroxide, tetrabutylphosphonium hydroxide, trimethylcyclohexylphosphonium chloride, trimethylcyclohexylphosphonium bromide, trimethylbenzylphosphonium chloride, trimethylbenzylphosphonium bromide, tetraphenylphosphonium bromide, triphenylmethylphosphonium bromide, triphenylmethylphosphonium iodide, triphenylethylphosphonium chloride, triphenylethylphosphonium bromide, triphenylethylphosphonium iodide, triphenylbenzylphosphonium chloride, and triphenylbenzylphosphonium bromide.
Among the catalysts listed above, 4-(dimethylamino)pyridine, 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]-7-undecene, 1,5-diazabicyclo[4,3,0]-5-nonene, 2-ethyl-4-methylimidazole, tris(p-tolyl)phosphine, tricyclohexylphosphine, tri(tert-butyl)phosphine, and tris(p-methoxyphenyl)phosphine are preferred, and 4-(dimethylamino)pyridine, 1,8-diazabicyclo[5,4,0]-7-undecene, 1,5-diazabicyclo[4,3,0]-5-nonene, and 2-ethyl-4-methylimidazole are particularly preferred. The catalysts may be used alone or in combination of two or more.
The amount of the catalyst used is in the range of 0.001 to 3% by weight based on the amount of the reaction substrate used in the reaction to obtain an epoxy resin obtained by reacting an ester compound represented by general formula (1). When these compounds are used as catalysts, they remain as catalyst residues in the obtained curable composition, which may deteriorate the insulating properties of the printed wiring board or shorten the pot life of the composition. Therefore, when a compound containing nitrogen is used as a catalyst, the nitrogen content in the curable composition is preferably 2000 ppm or less, more preferably 1000 ppm or less. When a compound containing phosphorus is used as a catalyst, the phosphorus content in the curable composition is preferably 2000 ppm or less, more preferably 1000 ppm or less.

In the synthesis reaction step of producing an epoxy resin obtained by reacting an ester compound represented by the general formula (1) according to the present invention, a solvent for the reaction may be used, and the solvent is not limited as long as it dissolves the epoxy resin. For example, aromatic hydrocarbon solvents, ketone solvents, amide solvents, glycol ether solvents, etc. may be mentioned. Only one type of solvent may be used, or two or more types may be used in combination.
Specific examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, etc. Specific examples of ketone solvents include acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, 2-heptanone, 4-heptanone, 2-octanone, cyclohexanone, acetylacetone, dioxane, etc.
Specific examples of amide solvents include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, 2-pyrrolidone, and N-methylpyrrolidone.
Specific examples of glycol ether solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol mono-n-butyl ether, and propylene glycol monomethyl ether acetate.

The solid content in the synthesis reaction during the production of the epoxy resin is preferably 10 to 95% by weight. If a highly viscous product is produced during the reaction, the reaction can be continued by adding additional solvent. After the reaction is completed, the solvent can be removed or further added as necessary.
In the production of epoxy resins, the polymerization reaction is carried out at a reaction temperature at which the catalyst used does not decompose. If the reaction temperature is too high, the catalyst may decompose, causing the reaction to stop, or the epoxy resin produced may deteriorate. Conversely, if the temperature is too low, the reaction may not proceed sufficiently. For these reasons, the reaction temperature is preferably 50 to 250°C, more preferably 120 to 230°C. The reaction time is usually 1 to 12 hours, preferably 3 to 10 hours. When a low-boiling point solvent such as acetone or methyl ethyl ketone is used, a reaction temperature higher than the boiling point under normal pressure can be ensured by carrying out the reaction under high pressure using an autoclave.

<Compound Having Radically Polymerizable Substituent>
The compound having a radically polymerizable substituent used in the curable composition of the present invention may be any conventionally known compound. Specific examples include one or more compounds selected from the group consisting of diallyl phthalate resins, diallyl phthalate compounds, polyphenylene ether resins having a radically polymerizable substituent, and vinyl compounds.
The diallyl phthalate resin, the diallyl phthalate compound, the polyphenylene ether resin having a radically polymerizable substituent, and the vinyl compound may be any compound including conventionally known compounds.

<Content of Thermosetting Compound and/or Compound Having Radically Polymerizable Substituent>
In the curable composition of the present invention, the content of the thermosetting compound and/or the compound having a radically polymerizable substituent is preferably in the range of 50 to 500 parts by weight, more preferably in the range of 50 to 400 parts by weight, still more preferably in the range of 50 to 300 parts by weight, and particularly preferably in the range of 50 to 200 parts by weight, relative to 100 parts by weight of the ester compound represented by general formula (1).
That is, as an embodiment of the curable composition of the present invention, in the case of an embodiment containing an ester compound represented by general formula (1) and a thermosetting compound, it means that the ester compound represented by general formula (1) contains the thermosetting compound in the above range per 100 parts by weight, in the case of an embodiment containing an ester compound represented by general formula (1) and a compound having a radical polymerizable substituent, it means that the ester compound represented by general formula (1) contains the compound having a radical polymerizable substituent in the above range per 100 parts by weight, and in the case of an embodiment containing an ester compound represented by general formula (1), a thermosetting compound, and a compound having a radical polymerizable substituent, it means that the ester compound represented by general formula (1) contains the thermosetting compound and the compound having a radical polymerizable substituent in the above range as a total amount per 100 parts by weight.
In addition, when an ester compound represented by general formula (2) is used in combination, the content is read as the content per 100 parts by weight of the total amount of the ester compound represented by general formula (1) and the ester compound represented by general formula (2).

<Additives>
The curable composition of the present invention may further contain various additives, as necessary, such as an ultraviolet inhibitor, an antioxidant, a coupling agent, a plasticizer, a flux, a flame retardant, a colorant, a dispersant, an emulsifier, an elasticity reducing agent, a diluent, an antifoaming agent, an ion trapping agent, an inorganic filler, an organic filler, etc. The type and amount of the additives used may be appropriately adjusted depending on the purpose of use.

<Curing Agent>
The curable composition of the present invention may further comprise a curing agent.
When an epoxy resin is used as a component of the curable composition of the present invention, the term "curing agent" includes the meaning of a substance that contributes to the crosslinking reaction and/or chain extension reaction between epoxy groups of the epoxy resin. In this case, even a substance that is usually called a "curing accelerator" is included in the curing agent as long as it contributes to the crosslinking reaction and/or chain extension reaction between epoxy groups of the epoxy resin.

The amount of the curing agent used is preferably 0.1 to 100 parts by weight, more preferably 80 parts by weight or less, and even more preferably 60 parts by weight or less, based on 100 parts by weight of the total amount of the ester compound represented by general formula (1) and the thermosetting resin or the compound having a radically polymerizable substituent.
The curing agent to be used is not particularly limited, and any agent generally known as a curing agent for a thermosetting resin or a compound having a radically polymerizable substituent can be used.

Specific examples of curing agents used in the curable composition of the present invention when an epoxy resin is used include phenol-based curing agents, amide-based curing agents, imidazoles, and active ester-based curing agents, which are preferred from the viewpoint of increasing heat resistance. Examples of phenol-based curing agents, amide-based curing agents, imidazoles, active ester-based curing agents, and other usable curing agents are listed below.

(Phenol-based hardener)
It is preferable to use a phenol-based curing agent as the curing agent from the viewpoints of improving the handleability of the resulting curable composition and the heat resistance of the cured product after curing. Specific examples of phenol-based hardeners include bisphenol A, bisphenol F, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl ether, 1,4-bis(4-hydroxyphenoxy)benzene, 1,3-bis(4-hydroxyphenoxy)benzene, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, phenol novolac, bisphenol A novolac, o-cresol novolac, m-cresol novolac, p-cresol novolac, xylenol novolac, poly-p-hydroxystyrene, hydroquinone, resorcinol, catechol, t-butylcatechol, Examples of the allylated pyrogallol include t-butyl hydroquinone, fluoroglycinol, pyrogallol, t-butyl pyrogallol, allylated pyrogallol, polyallylated pyrogallol, 1,2,4-benzenetriol, 2,3,4-trihydroxybenzophenone, 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,4-dihydroxynaphthalene, 2,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,8-dihydroxynaphthalene, allylated products or polyallylated products of the above dihydroxynaphthalenes, allylated bisphenol A, allylated bisphenol F, allylated phenol novolak, and allylated pyrogallol.

The phenol-based hardeners listed above may be used alone or in any combination and ratio of two or more. When the hardener is a phenol-based hardener, it is preferable to use it so that the equivalent ratio of the functional groups in the hardener to the epoxy groups in the epoxy resin is in the range of 0.8 to 1.5. This range is preferable because it is less likely that unreacted epoxy groups or functional groups of the hardener will remain.

(Amide-based hardener)
It is preferable to use an amide-based curing agent as the curing agent from the viewpoint of improving heat resistance, etc. It is preferable to use an amide-based curing agent as the curing agent from the viewpoint of improving the heat resistance of the obtained curable composition. Examples of the amide-based curing agent include dicyandiamide and its derivatives, polyamide resins, etc. Specific examples of the amide-based curing agent include "LUCKAMIDE" N-153-IM-65, EA-330, and TD-960 (manufactured by DIC Corporation).

The amide-based hardeners listed above may be used alone or in any combination and ratio of two or more. The amide-based hardener is preferably used in an amount ranging from 0.1 to 20% by weight based on the total weight of the epoxy resin and amide-based hardener used in the hardenable composition.

(Imidazoles)
It is preferable to use imidazoles as the curing agent from the viewpoint of sufficiently progressing the curing reaction and improving heat resistance. Examples of imidazoles include 2-phenylimidazole, 2-ethyl-4(5)-methylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyano-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl- Examples of the imidazoles include 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and adducts of epoxy resins and the above imidazoles. Since imidazoles have catalytic activity, they can generally be classified as curing accelerators, which will be described later, but in the present invention, they are classified as curing agents.
The imidazoles listed above may be used alone or in any combination and ratio of two or more. The imidazoles are preferably used in an amount of 0.1 to 20% by weight based on the total weight of the epoxy resin and the imidazoles used in the curable composition.

(Active ester curing agent)
The use of an active ester-based curing agent as a curing agent is preferable from the viewpoint of reducing the water absorption of the obtained cured product. As the active ester-based curing agent, a compound having two or more highly reactive ester groups in one molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, is preferable, and among them, phenol esters obtained by reacting a carboxylic acid compound with an aromatic compound having a phenolic hydroxyl group are more preferable. Specific examples of the carboxylic acid compound include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of aromatic compounds having a phenolic hydroxyl group include catechol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadienyldiphenol, and phenol novolac. In addition, an ester compound represented by the general formula (2) according to the present invention can also be used.
The active ester curing agents listed above may be used alone or in any combination and ratio of two or more. The active ester curing agent is preferably used so that the equivalent ratio of the active ester group in the curing agent to the epoxy group in the epoxy resin used in the curable composition is in the range of 0.2 to 2.0.

(Other hardeners)
Curing agents that can be used in the curable composition of the present invention, other than phenol-based curing agents, amide-based curing agents, and imidazoles, include, for example, amine-based curing agents (excluding tertiary amines), acid anhydride-based curing agents, tertiary amines, organic phosphines, phosphonium salts, tetraphenylboron salts, organic acid dihydrazides, boron halide amine complexes, polymercaptan-based curing agents, isocyanate-based curing agents, blocked isocyanate-based curing agents, etc. The other curing agents listed above may be used alone or in any combination and ratio of two or more.
Furthermore, examples of the curing agent that can be used when a compound having a radical polymerizable group is used include ionic catalysts such as imidazoles, tertiary amines, quaternary ammonium salts, boron trifluoride amine complexes, organophosphines, and organophosphonium salts; organic peroxides such as di-t-butyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, dicumyl peroxide, and t-butyl peroxybenzoate; and radical polymerization initiators such as hydroperoxides and azoisobutyronitrile.

In the curable composition of the present invention, when an epoxy resin obtained by reacting an ester compound represented by general formula (1) and another compound (a thermosetting compound other than an epoxy resin obtained by reacting an ester compound represented by general formula (1) or a compound having a radical polymerizable substituent) are used as one component of the thermosetting compound, the amount of the other compound in the total epoxy resin component as a solid content is preferably 1% by weight or more, more preferably 5% by weight or more, and even more preferably 10% by weight or more, while it is preferably 99% by weight or less, more preferably 95% by weight or less, and even more preferably 90% by weight or less. By having the ratio of the other compound be equal to or more than the above lower limit, the effect of improving physical properties by blending the other compound can be sufficiently obtained. On the other hand, by having the ratio of the other compound be equal to or less than the above upper limit, the effect of the epoxy resin of the present invention is sufficiently exhibited, which is preferable from the viewpoint of obtaining film formability.

<Solvent>
The curable composition of the present invention may be diluted by further blending a solvent in order to appropriately adjust the viscosity of the curable composition when handling it for forming a coating film. In the curable composition of the present invention, the solvent is used to ensure the handleability and workability in molding the curable composition, and there is no particular limit to the amount of the solvent used.

Solvents that may be contained in the curable composition of the present invention include, for example, ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone, etc., esters such as ethyl acetate, etc., ethers such as ethylene glycol monomethyl ether, amides such as N,N-dimethylformamide, N,N-dimethylacetamide, etc., alcohols such as methanol, ethanol, etc., alkanes such as hexane, cyclohexane, etc., aromatics such as toluene, xylene, etc. The above-mentioned solvents may be used alone or in any combination and ratio of two or more.

<Cured Product>
The cured product obtained by curing the curable composition of the present invention has excellent dielectric properties and heat resistance. The term "curing" used here means intentionally curing the epoxy resin composition by heat and/or light, and the degree of curing may be controlled depending on the desired physical properties and applications. The degree of progress may be completely cured or semi-cured, and is not particularly limited, but the reaction rate of the curing reaction is usually 5 to 95%.

<Curing method>
The curing method of the curable composition of the present invention varies depending on the components and their amounts in the curable composition, but typically includes heating conditions of 80 to 280° C. for 60 to 360 minutes. This heating is preferably performed in two stages, with a primary heating at 80 to 160° C. for 10 to 90 minutes and a secondary heating at 120 to 200° C. for 60 to 150 minutes, and in a compounding system in which the glass transition temperature (Tg) exceeds the temperature of the secondary heating, it is preferable to further perform a tertiary heating at 150 to 280° C. for 60 to 120 minutes. Performing the secondary and tertiary heating in this manner is preferable from the viewpoint of reducing poor curing and residual solvent.
When preparing a semi-cured resin product, it is preferable to proceed with the curing reaction of the curable composition to such an extent that the shape can be maintained by heating, etc. When the curable composition contains a solvent, most of the solvent is usually removed by a technique such as heating, reducing pressure, or air drying, but 5% by mass or less of the solvent may remain in the semi-cured resin product.

<Applications>
The epoxy resin obtained by reacting the ester compound represented by the general formula (1) according to the present invention has excellent film-forming properties, and is therefore applicable to various fields such as adhesives, paints, civil engineering and construction materials, and insulating materials for electric and electronic parts, and is particularly useful as insulating casting, laminating materials, sealing materials, etc. in the electric and electronic fields.
Examples of applications of the epoxy resin obtained by reacting the ester compound represented by general formula (1) according to the present invention, and the curable composition of the present invention and its cured product include film-like adhesives, liquid adhesives, composite materials, paints, civil engineering and building materials, insulating materials for electric and electronic parts, multilayer printed wiring boards, laminates for electric and electronic circuits such as capacitors, semiconductor encapsulating materials, underfill materials, interchip fills for 3D-LSI, insulating sheets, prepregs, heat dissipation substrates, insulating castings, and the like, but are not limited to these.

(Laminates for electrical and electronic circuits)
As described above, the curable composition of the present invention can be suitably used for the application of laminates for electric and electronic circuits. In the present invention, the term "laminated plate for electric and electronic circuits" refers to a laminate in which a layer containing the curable composition of the present invention and a conductive metal layer are laminated, and is used as a concept including, for example, a capacitor, even if it is not an electric or electronic circuit, as long as the layer containing the curable composition of the present invention and a conductive metal layer are laminated. In addition, layers consisting of two or more types of curable compositions may be formed in the laminate for electric and electronic circuits, and it is sufficient that the curable composition of the present invention is used in at least one layer. In addition, two or more types of conductive metal layers may be formed.
In the laminate for electric/electronic circuits, the layer made of the curable composition usually has a thickness of about 10 to 200 μm, and the conductive metal layer usually has a thickness of about 0.2 to 70 μm.

(Conductive metal)
Examples of the conductive metal in the laminate for electric/electronic circuits include metals such as copper and aluminum, and alloys containing these metals. In the present invention, the conductive metal layer of the laminate for electric/electronic circuits may be a metal foil of these metals, or a metal layer formed by plating or sputtering.

(Method of manufacturing laminates for electrical and electronic circuits)
The laminate for electric/electronic circuits of the present invention can be produced, for example, by the following method.
(1) A nonwoven fabric, cloth, or the like using inorganic and/or organic fiber materials such as glass fiber, polyester fiber, aramid fiber, cellulose, nanofiber cellulose, etc. is impregnated with the curable composition of the present invention to form a prepreg, and a conductive metal layer is provided by conductive metal foil and/or plating, after which a circuit is formed using a photoresist or the like, and the required number of such layers are stacked to form a laminate.
(2) The prepreg of (1) above is used as a core material, and a layer of a curable composition and a conductive metal layer are laminated on one or both sides of the core material. The layer of the curable composition may contain organic and/or inorganic fillers.
(3) A laminate for electric/electronic circuits is produced by alternately laminating layers of a curable composition and conductive metal layers without using a core material.
According to the present invention, it is possible to provide a cured product having excellent heat resistance and dielectric properties.
For this reason, the curable composition of the present invention can be applied in various fields, such as film-like adhesives, liquid adhesives, composite materials, paints, civil engineering and building materials, insulating materials for electric and electronic components, multilayer printed wiring boards, laminates for electric and electronic circuits such as capacitors, semiconductor encapsulation materials, underfill materials, interchip fills for 3D-LSIs, insulating sheets, prepregs, heat dissipation substrates, and insulating casting, and is particularly useful as insulating casting, laminate materials, encapsulation materials, and the like in the electric and electronic fields.

The present invention will now be described more specifically with reference to examples.
<Analysis method>
1. Reaction solution composition and purity analysis (ultra-performance liquid chromatography: UFLC)
0.01 g of the ester compound synthesized in the Examples was weighed into a 50 mL measuring flask and diluted with acetonitrile.
The prepared sample was subjected to purity analysis by high performance liquid chromatography as described below.
Purity analysis (analysis value is area percentage)
Measurement device: High-performance liquid chromatography analyzer Prominence UFLC (manufactured by Shimadzu Corporation)
Pump: LC-20AD
Column oven: CTO-20A
Detector: SPD-20A
Column: HALO-C18 (inner diameter 3 mm, length 75 mm)
Oven temperature: 50°C
Flow rate: 0.7 mL/min.
Mobile phase: (A) 0.1% by volume acetic acid aqueous solution, (B) acetonitrile Gradient conditions: (A) Volume % (time from start of analysis) 30% (2.0 min.) → 100% (15.0 min.) → 100% (18.0 min.)
Sample injection volume: 7 μL
Detection wavelength: 254 nm
2. Evaluation of Curing Characteristics The curing characteristics of the synthesized epoxy resin compositions were evaluated by differential scanning calorimetry (DSC) under the following operating conditions: The exothermic peak temperature was taken as the curing temperature.
[Measurement condition]
Apparatus: DSC7020/Hitachi High-Tech Science Co., Ltd. Heating rate: 10° C./min.
Measurement temperature range: 30 to 350°C
Measurement atmosphere: Nitrogen 50 mL/min.
Measurement sample: 3 mg of synthesized epoxy resin composition
3. Measurement of glass transition temperature (Tg) (dynamic mechanical analysis (DMA))
Apparatus: DMA850/manufactured by TA Instruments Japan, Inc. Measurement conditions: 3-point bending Measurement temperature: 30 to 310°C
Measurement frequency: 1.0 (Hz)
Sample dimensions: (60mm x 15mm x 2mm)
Heating rate: 1.0° C./min.
4. Evaluation of Dielectric Properties The films (sample size: width 1.5 mm, length 8.0 mm) prepared in the examples and comparative examples were measured for relative dielectric constant and dielectric loss tangent using the following device (sample size: width 1.5 mm, length 8.0 mm).
Measurement device: PNA network analyzer N522B (manufactured by Keysight Technologies, Inc.)
Cavity resonator: CP531 for 10 GHz (manufactured by Kanto Electronics Application Development Co., Ltd.)
[Measurement condition]
Test method: Compliant with IEC 62180 (cavity resonator perturbation method)
Test conditions: Frequency: 10 GHz
Number of measurements: n = 2

Example 1 (Synthesis of ester compound (p-151) represented by the following chemical formula 1-1)

A 1000 mL four-neck flask equipped with a thermometer, a stirrer, a cooling tube, and a dropping funnel was charged with 465 g (1.50 moles) of bisphenol TMC and 352 g of acetic anhydride, and the inside of the reaction vessel was replaced with nitrogen, and the temperature of the mixed solution was set to 130°C. Then, the mixture was stirred at 130°C for 6 hours. As a result of analyzing the composition of the reaction solution by UFLC according to the above analytical method, the proportion of 1,1-bis(4-acetoxyphenyl)-3,3,5-trimethylcyclohexane present in the reaction solution was 96 area %. After the reaction was completed, acetic anhydride and the produced acetic acid were removed by distillation under reduced pressure at 130°C. The pressure during distillation was gradually reduced to 1.5 kPa. 560 g of a composition containing 1,1-bis(4-acetoxyphenyl)-3,3,5-trimethylcyclohexane (purity: 99.9%) was obtained.
From the results of ¹ H-NMR analysis, it was confirmed that 1,1-bis(4-acetoxyphenyl)-3,3,5-trimethylcyclohexane was obtained.
¹ H-NMR analysis (400 MHz, solvent: CDCl ₃ , standard substance: tetramethylsilane)
0.40 (3H,s), 0.85-0.89 (1H,t), 0.96-0.97 (6H,d), 1.14-1.20 (1H,t), 1.37-1.40 (1H,d), 1.56 (2H,s), 1.92-2.10 (2H,m), 2.25-2.27 (6H,d), 2.42-2.45 (1H,d), 2.64-2.68 (1H,d), 6.90-6.92 (2H,d), 6.98-7.00 (2H,d), 7.18-7.20 (2H,d), 7.31-7.34 (2H,d).
In a 3000 mL four-neck flask equipped with a thermometer, a stirrer, a cooling tube, and a dropping funnel, 300 g (0.76 mol) of 1,1-bis(4-acetoxyphenyl)-3,3,5-trimethylcyclohexane, 213 g of furan carboxylic acid, 4.0 g of 4-dimethylaminopyridine, and 1500 g of diphenyl ether were charged, and the inside of the reaction vessel was replaced with nitrogen, and the temperature of the mixed solution was set to 230° C. Thereafter, the mixture was stirred at 230° C. for 8 hours while a liquid containing acetic acid and the solvent diphenyl ether, etc., which was generated as the reaction proceeded, was distilled out of the system. As a result of analyzing the composition of the reaction solution by UFLC using the above analytical method, the proportion of the target compound present in the reaction solution was 52 area %. After the reaction was completed, the generated acetic acid, diphenyl ether, and furan carboxylic acid were removed by reduced pressure distillation under the condition of 210° C. The pressure during distillation was gradually reduced to 5.0 kPa. After cooling the concentrated diphenyl ether solution containing the target compound, 845 g of 1-butanol was added. Thereafter, the mixture was cooled to 70°C to precipitate crystals. 229 g of 1-butanol was added, and the mixture was cooled to 30°C. The obtained slurry containing the target compound was subjected to solid-liquid separation by centrifugal filtration, and the obtained crystals containing the solvent were dried at 80°C and 2.0 kPa to obtain 337 g of the target compound (1-1) (purity: 99.8%). In addition, as a result of differential scanning calorimetry (DSC), it was revealed that the target compound was a crystal having a maximum endothermic peak temperature of 183.5°C. The DSC data is shown in FIG. 1.
From the results of ¹ H-NMR analysis, it was confirmed that the target compound having the above structure was obtained.
¹ H-NMR analysis (400 MHz, solvent: CDCl ₃ , standard substance: tetramethylsilane)
0.39 (3H,s), 0.81-0.92 (1H,t), 0.98-1.00 (6H,d), 1.18-1.24 (1H,t), 1.39-1.42 (1H,d), 1.56 (4H,s), 1.96-2.10 (2H,m), 2.46-2.49 (1H,d), 2.68-2.72 (1H,d), 6.57-6.59 (2H,m), 7.04-7.06 (2H,d), 7.13-7.15 (2H,d), 7.24-7.33 (1H,m), 7.34-7.40 (4H,m), 7.65-7.67 (2H,m).
The target compound thus obtained had a solubility of 20 to 40% by weight in each of the solutions in methyl ethyl ketone, cyclohexanone, and N-methylpyrrolidone, and a solubility of 10 to 20% by weight in each of the solutions in toluene, propylene glycol monomethyl ether acetate, and ethyl acetate, confirming that the target compound had excellent solvent solubility.

Example 2 (Synthesis of ester compound (p-28) represented by the following chemical formula 1-2)

After synthesizing diacetyl biphenol by acetylating biphenol in the same manner as in Example 1, 70 g (0.26 mol) of diacetyl biphenol, 72 g of furan carboxylic acid, 1.4 g of 4-dimethylaminopyridine, and 431 g of diphenyl ether were charged into a 1000 mL four-neck flask equipped with a thermometer, a stirrer, a cooling tube, and a dropping funnel, and the inside of the reaction vessel was replaced with nitrogen, and the temperature of the mixed solution was set to 210°C. Thereafter, the mixture was stirred at 210°C for 4 hours while distilling out of the system a liquid containing acetic acid and the solvent diphenyl ether, etc., which were generated as the reaction proceeded, under reduced pressure conditions. The pressure during distillation was gradually reduced, and finally set to 25.0 kPa. The composition of the reaction solution was analyzed by UFLC using the above analytical method, and the proportion of the target compound present in the reaction solution was 69 area %. After the reaction was completed, the mixture was cooled to 30°C to precipitate crystals. The obtained slurry containing the target compound was subjected to solid-liquid separation by centrifugal filtration, and the obtained crystals containing the solvent were dried at 80°C and 2.0 kPa to obtain 81 g of the target compound (1-2) (purity: 99.7%). In addition, as a result of differential scanning calorimetry (DSC), it was revealed that the target compound was a crystal having a maximum endothermic peak temperature of 240.0°C. The DSC data is shown in Figure 2.
From the results of ¹ H-NMR analysis, it was confirmed that the target compound having the above structure was obtained.
¹ H-NMR analysis (400 MHz, solvent: CDCl ₃ , standard substance: tetramethylsilane)
6.82-6.83 (2H,dd), 7.37-7.40 (4H,dt), 7.60-7.61 (2H,dd), 7.76-7.80 (4H,dt), 8.13 (2H,s).

Example 3 (Synthesis of ester compound (p-148) represented by the following chemical formula 1-3)

In the same manner as in Example 1, 4,4'-dihydroxy-2,2',3,3',5,5'-hexamethylbiphenyl was acetylated to synthesize 4,4'-diacetoxy-2,2',3,3',5,5'-hexamethylbiphenyl, and then 204 g (0.58 moles) of 4,4'-diacetoxy-2,2',3,3',5,5'-hexamethylbiphenyl was charged into a 2000 mL four-neck flask equipped with a thermometer, a stirrer, a cooling tube, and a dropping funnel, and after replacing the atmosphere in the reaction vessel with nitrogen, the temperature of the mixed solution was set to 220°C. Thereafter, the mixture was stirred at 220°C for 14 hours while distilling out of the system a liquid containing acetic acid and the solvent diphenyl ether produced as the reaction proceeded. As a result of analyzing the composition of the reaction solution by UFLC using the above analytical method, the ratio of the target compound present in the reaction solution was 70 area %. After the reaction was completed, the produced acetic acid, diphenyl ether, and furan carboxylic acid were removed by vacuum distillation under the condition of 220 ° C. The pressure during distillation was gradually reduced to 5.0 kPa. After cooling the diphenyl ether solution containing the target compound after concentration, 88 g of isopropanol and 149 g of diphenyl ether were added. Then, it was cooled to 30 ° C. to precipitate crystals. The obtained slurry containing the target compound was subjected to solid-liquid separation by centrifugal filtration, and the obtained crystals containing the solvent were dried at 60 ° C. and 2.0 kPa to obtain 233 g of the target compound (purity: 99.4%). In addition, it was revealed that the target compound was a crystal with a maximum endothermic peak temperature of 237.7 ° C. as a result of differential scanning calorimetry (DSC). The DSC data is shown in FIG. 3.
From the results of ¹ H-NMR analysis, it was confirmed that the target compound having the above structure was obtained.
¹ H-NMR analysis (400 MHz, solvent: C ₂ D ₆ OS, standard substance: tetramethylsilane)
1.94 (3H,s), 2.09 (6H,s), 2.11 (6H,s), 6.84-6.85 (2H,dd), 6.93 (2H,s), 7.67-7.68 (2H,dd), 8.15-8.15 (2H,d).

Example 4
10.0 g of the compound (1-1) synthesized in Example 1, 10.1 g of a dicyclopentadiene type epoxy resin (XD-1000, manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 251 g/eq.), 0.2 g of 4-dimethylaminopyridine, and 16.2 g of methyl ethyl ketone were charged into a 100 mL beaker, heated at 70°C, and dissolved. The solution was cast onto a release film and air-dried at room temperature. After that, the mixture was dried in a vacuum dryer at 80°C and 1.5 kPa, and then crushed to obtain a composition powder containing the compound (1-1) and an epoxy resin. The composition powder was packed into a silicone resin mold and cured at 140°C/1 hour, 150°C/1 hour, 160°C/1.5 hours, 180°C/1.5 hours, and 250°C/2 hours. The glass transition point (Tg) of the cured product obtained by the above analysis method was measured and found to be 250.0°C.

Example 5
A mixture of 5.1 g of the compound (1-1) synthesized in Example 1 and 5.0 g of 1,1-bis(4-acetoxyphenyl)-3,3,5-trimethylcyclohexane synthesized in Example 1, 11.4 g of dicyclopentadiene type epoxy resin (XD-1000, manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 251 g/eq.), 0.2 g of 4-dimethylaminopyridine, and 11.1 g of methyl ethyl ketone were charged in a 100 mL beaker and dissolved by heating at 70°C. The solution was cast on a release film and air-dried at room temperature. Thereafter, the mixture was dried in a vacuum dryer at 80°C and 1.5 kPa, and then crushed to obtain a composition powder containing the compound (1-1), 1,1-bis(4-acetoxyphenyl)-3,3,5-trimethylcyclohexane, and an epoxy resin. The composition powder was packed into a silicone resin mold and cured at 140° C./1 hour, 150° C./1 hour, 160° C./1.5 hours, and 180° C./1.5 hours. The glass transition temperature (Tg) of the cured product obtained was measured by the above-mentioned analytical method and was found to be 206.3° C.
It was clear from Examples 4 and 5 that the heat resistance was higher when the proportion of the compound represented by general formula (1) was higher.

Example 6
20.0 g of the compound (1-1) synthesized in Example 1, 16.0 g of orthocresol novolac epoxy resin (manufactured by DIC Corporation: trade name "Epiclon N-673"), and 40.0 g of methyl ethyl ketone were charged into a 100 mL beaker and stirred to dissolve. 0.72 g of 4-dimethylaminopyridine was added to the solution and further stirred to dissolve 4-dimethylaminopyridine. After complete dissolution, the solution was transferred to a tray and dried overnight in a draft, and then dried in a vacuum dryer at 60°C and 1.5 kPa for 5 hours. The obtained composition was then added to a mold (φ100 mm press mold) and heated in a heat press tester at 3 MPa under conditions of 160°C/2 hours and 180°C/2 hours to obtain a cured product.

<Comparative Example 1>
10.0 g of a novolac type curing agent (manufactured by AICA Corporation, product name "BRG-555"), 20.0 g of an orthocresol novolac type epoxy resin (manufactured by DIC Corporation, product name "Epiclon N-673"), and 40.0 g of methyl ethyl ketone were charged into a 100 mL beaker and stirred to dissolve. 0.60 g of triphenylphosphine was added to the solution and further stirred to dissolve the triphenylphosphine. After complete dissolution, the solution was transferred to a tray. After drying overnight in a draft, the mixture was dried in a vacuum dryer at 60°C and 1.5 kPa for 5 hours. The resulting composition was then added to a mold (φ100 mm press mold) and heated in a heat press tester at 3 MPa under the conditions of 100°C/1 hour and 130°C/2 hours. The cured product was then heated in a hot air circulation oven under the conditions of 140°C/2 hours, 150°C/2 hours, 160°C/2 hours, and 180°C/2 hours to obtain a cured product.

The glass transition temperature (Tg) and dielectric properties of the cured products obtained in Example 6 and Comparative Example 1 were evaluated by the above-mentioned analytical methods. The results are summarized in Table 1.

As shown above, it was revealed that the epoxy resin cured product using the compound of Example 1, which is the compound of the present invention, as a curing agent has a high glass transition temperature and exhibits high heat resistance. It was also revealed that it exhibits excellent dielectric properties.
The ester compound of the present invention is blended with an epoxy resin, and the cured product obtained by curing the epoxy resin has excellent heat resistance and dielectric properties. It is presumed that the ester compound represented by the general formula (1) reacts with the epoxy resin as a curing agent and esterifies the secondary hydroxyl group generated by the reaction of the epoxy resin with the curing agent, thereby suppressing polarization of the cured product and exhibiting excellent dielectric properties.
Therefore, the epoxy resin composition containing the ester compound of the present invention is applicable in various fields such as adhesives, coating materials, civil engineering and construction materials, and insulating materials for electric and electronic parts, and is particularly useful as insulating casting materials, laminating materials, sealing materials, and the like in the electric and electronic fields.
Examples of applications of the ester compound of the present invention and the epoxy resin composition containing the same include multilayer printed wiring boards, laminates for electric/electronic circuits such as capacitors, adhesives such as film-like adhesives and liquid adhesives, semiconductor encapsulating materials, underfill materials, interchip fills for 3D-LSIs, insulating sheets, prepregs, and heat dissipation substrates, but are not limited thereto.

Claims

An ester compound represented by general formula (3):

(In the formula, each R2 independently represents a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms, each R3 independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and Y represents a divalent group represented by general formula (3a) or general formula (3b).

(In general formulas (3a) and (3b), R 1 's each independently represent an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and * represents a bonding position. In general formula (3a), m's each independently represent an integer of 1 to 4. In general formula (3b), n's each independently represent 0 or an integer of 1 to 4, and Z's each independently represent a cycloalkylidene group having 7 to 20 carbon atoms.)
The ester compound according to claim 1 , wherein both R 2s in the ester compound represented by the general formula (3) are single bonds.
The ester compound according to claim 2, wherein both R 3 of the ester compound represented by the general formula (3) are hydrogen atoms.
The ester compound according to claim 3, wherein the ester compound represented by the general formula (3) is compound (p-139), (p-142), (p-145), (p-148), (p-151), (p-154) or (p-172).
A crystal of an ester compound of the compound (p-148) described in claim 4.
A crystal of the ester compound of compound (p-148) according to claim 5, the maximum endothermic peak temperature of which is in the range of 234 to 240°C as determined by differential scanning calorimetry.
A crystal of an ester compound of the compound (p-151) described in claim 4.
A crystal of the ester compound of compound (p-151) according to claim 7, which has a maximum endothermic peak temperature in the range of 180 to 188°C as determined by differential scanning calorimetry.
An ester compound composition for use as a resin raw material, comprising an ester compound represented by the general formula (3) according to claim 1 and an ester compound represented by the general formula (2).

(In the formula, each R 1 independently represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, each R 6 independently represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, each X independently represents a single bond, an oxygen atom, a sulfur atom, a sulfonyl group, a carbonyl group, or a divalent group represented by general formula (1a), (1b), or (1c), and each n independently represents 0 or an integer of 1 to 4.)

(In general formulas (1a), (1b) and (1c), R 4 and R 5 each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms; R 4 and R 5 may be bonded to each other to form a cycloalkylidene group having 5 to 20 carbon atoms as a whole; Ar 1 and Ar 2 each represent an aryl group having 6 to 12 carbon atoms; and * each indicates a bonding position.)
The ester compound composition for resin raw material according to claim 9, which contains 0.1 to 400 parts by weight of the ester compound represented by the general formula (2) per 100 parts by weight of the ester compound represented by the general formula (3).
An epoxy resin obtained by reacting an ester compound represented by general formula (3) according to claim 1 with any one selected from an aromatic diglycidyl ether compound, a mixture containing an aromatic dihydroxy compound and epihalohydrin, and a phenoxy resin having an epoxy group obtained by polymerizing an aromatic dihydroxy compound and epihalohydrin.